Red List of South African Species

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Endangered (EN)
B1ab(ii,iii,v)+2ab(ii,iii,v)
Assessors: Bruce Ellender Albert Chakona Olaf Weyl
Facilitators: Dewidine Van Der Colff
Reviewers: Jörg Freyhof

Rationale

Pseudobarbus  sp. nov. 'Keiskamma' has a restricted geographic range as it is known from the headwater tributaries of the Keiskamma River System, in the Eastern Cape Province of South Africa. This species is known from five locations and is severely fragmented (small and isolated subpopulations). It is known from an area of occupancy (AOO) of 80 km2 (calculated using a 2x2 km2 grid) and extent of occurrence (EOO) of 354 km2  which is experiencing continuous decline due to deterioration in habitat quality and spread of invasive alien species, particularly Largemouth Bass (Micropterus salmoides), Smallmouth Bass (M. dolomieu), Rainbow Trout (Oncorhynchus mykiss) and Brown Trout (Salmo trutta). The presence of the alien African Sharptooth Catfish (Clarias gariepinus) in the area is a more recent additional but unquantified threat. Pseudobarbus sp. nov. 'Keiskamma' is listed as Endangered B1ab(ii,iii,v)+2ab(ii,iii,v).

Distribution

Pseudobarbus sp. nov. 'Keiskamma' is restricted to the tributaries of the Keiskamma River System (the Tyume, Amatele, Mnyameni, Rabula and Wolf  rivers), Eastern Cape, South Africa (Ellender 2013).

Population trend

Trend

The lineage has a very limited distribution, with small known population sizes that are under severe threat from invasive alien fish species and habitat degradation. These small subpopulation are confined to small stretches of the river due to the presence of invasive alien species, resulting in severely fragmented subpopulations. Quantitative data are available from a comprehensive assessment of the distribution of this lineage in the upper Keiskamma River System by Ellender (2013) which demonstrate that the Wolf and Cata River subpopulations have been extirpated. A remnant subpopulation occurs in the Tyume River above Binfield Dam, but the lineage is absent from the dam and the river below.

Threats

Loss of habitat and alien invasive fish species are the two major threats. In an assessment of the upper Keiskamma River System, Ellender (2013) demonstrated that this lineage had been replaced by trout in 24% of its distribution. Trout predation excluded Pseudobarbus sp. nov. 'Keiskamma' from headwater reaches and restricted them to the lower portions of the river where habitat degradation and interactions with alien African Sharptooth Catfish (Clarias gariepinus) and invasive species Largemouth Bass (Micropterus salmoides) and Smallmouth Bass (M. dolomieu) were potential threats. This is of concern as in the Keiskamma River System where Rainbow Trout (Oncorhynchus mykiss) has established in the Tyume, Amatele, Mnyameni and Wolf rivers, while Brown Trout (Salmo trutta) has established in the Cata River. Only one specimen of African Sharptooth Catfish was caught in the mainstream Keiskamma River. African Sharptooth Catfish has established in the lower Tyume (Mayekiso and Hecht 1988) and is probably in the early establishment phase in the upper Keiskamma River. Habitat degradation due to erosion and siltation is an additional threat.

Conservation

None known. Comprehensive surveys by Ellender (2013) indicated that Pseudobarbus sp. nov. 'Keiskamma' has been extirpated from the Cata and Wolf Rivers. Remnant subpopulations are highly fragmented and are now confined to small stretches of the rivers due to presence of alien fishes resulting in habitat loss. The strongest remaining subpopulation of this lineage occurs in the Tyume where it is restricted to a 10 km stretch of the river, but there are serious conservation concerns because this section of the river has been invaded by trout. Efforts are needed to thoroughly investigate the current distribution of this lineage in relation to invasions of its habitat by Largemouth and Smallmouth Bass. Immediate conservation measures are required to secure the remaining population of Pseudobarbus sp. nov. 'Keiskamma' through eradication of alien species (Ellender 2013).

References 

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,]
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